Telephone system



May l, 1928. 1,667,846 6 C. B. FOWLER ET AL 'TELE'PHONE SYSTEM Original Filed Dec. 23. 1926 sheetsfiheei 1 ,Nmvmm RENGf 0mm CHARZES W LucE/r May 1, 1928.

C. B. FOWLER ET AL TELEPHONE SYSTEM Original Filed D60. 23. 1926 2 Sheets-Sheet 2 CHARLES W ZUGEK Arrow/Er Patented May 1, 1928.

UNITED "STATES.

PATENT' OFFICE. v

CLARENCE B. rownnn, or QUEENS ILLAGE, Ann CHARLES w. tween, 01? ASTORIA,

NEW ORK, assrenonsrro BELL TELEPHONE LABORATORIES, INooBroi Ar-nn,

or new YORK, N. Y A conrona'rron or NEW YORK.

TELEPHONE SYSTEM.

Original application filed December 23, 1926, Serial No. 156,574. Divided and this application filed May 26,1927. Serial No. 194,312.

This application is a division of application Serial No. 156,574, filed December 23, 1926..

This invention relates to telephone systems and more particularly to straightforward trunking systems.

According to the invention a straightforward trunking system, in which a common control equipment is employed for the use of a plurality of trunks, is provided with means whereby a meter is o erated when the control equipment is actuated to control the trunk to which it is connected and means whereby, if the common control equipment has not been actuated, Said meter may be operated by the actuation of a busy back sig nal transn'iitting means. The arrangement is also such that the busy back signal transmitting means cannot operate the meter it the common control equipment has been actuated. That is, the meter can only be operated once for each connection of the common control equipment to a trunk either by the actuation of the common control equipment or by the busy back signal transmitting means.

This invention may be applied to a straightforward trunking system oithe kind described in the copending application of Horace V. Ulrich, Serial No. 156,570, filed December 23, 1926, or a similar system described in the copending application of Harold Cahill, Serial No. 151,631, filed November 30, 1926. In these two systems 'neans is provided whereby a ringing key equipment common to a plurality of trunks is adapted to be associated with the incoming end of any one of said trunks. This means operates if atrunk has been seized at its outgoing end and a key individual to this trunk has been actuated.

This invention has been illustrated in the accompanying drawings in which Fig. 1 shows a straightforward trunk of the toll switching trunk tyoej his trunk is shown terminating in a jack at a toll oper'ators position where a toll operators cord is shown for completing a connection between this toll switching trunk and another trunk shown leading to a distant ofii'ce where it may be extended to a calling subscriber. This ,sfliz ghtforiavard trunkis shown terminating in a plug at a B operators position and a called subscribers line has been shown in diagrammatic form. Fig. 2 shows a common ringing key equipment and an associated B operators telephone set which equipment may be associated with any one 01 a group of trunks to which the straightforward trunk shown in Fig. 1 belongs.

v Referring now to the drawings, if it is assumed that a toll operator at A has inserted a calling plug of cord 1 in jack 2 of trunk QT, the following description will relate to the association of the common ringing key equipment shown in Fig. 2 to this trunk and to the manipulation of the ringing keys in this circuit to prepare the usual ring ing equipment associated with the trunk ST for the transmission of ringing signals to a wanted subscribers line, such as 3. This description will be followed bya description of the invention as applied to this circuit, that is, how a busy signal may be transmitted back to the toll operators cord I and how the peg count meter may be actuated.

As trunk ST is seized it iswell known in the art how a loop circuit is established through cord lfor the operation of relay 5. Relay 5 when operated closes a circuit for the operation of relay 6 as "follows: battery, upper inner armature and back contact of relay 7, left hand winding of relay 6, armature and front contact of relay 5 to ground. Relay 5 in operating also closes a circuit for the operation or relays 8 and 9. The circuit for the operation of relay 9 is as follows: battery, make-before-break contact of busy back relay 10, inner left hand make-beforebreak contact of relayll, right hand winding of relay 9, lower inner armature and back contact of relay 7, armature and front contact of relay 5 to ground.

Relay 9 in operating closes a circuit for the dashing of the guard lamp 12 as follows: battery, lamp 12, inner right hand armature and front contact of relay 9, conductor 14 inner left-hand armature and back contact of relay 100, right hand windingof relay 101 to ground. "This circuit causes the lighting of lamp 12 and operation of relay .101. Relay 101 in operating closes an obvious circuit for the operation of the slow-to-operaterelay .1021 This relay in turn closer an obvious circuit for the slow-to operate relay 103. Relay 103 in tqierating closes an obvious circuit for the operation ol slow-to-operate relay 100 which in operating' inserts a resistance in the circuit for lamp 1:. and at the same time places a. shunt comprisin; the left hand winding of relay 101 ahout the said resistance and lamp 12 wherehy lamp 12 is now extinguished. On the operation of this relay 100. the circuit through the right hand winding of relay lot is extended through the imtke-hetorchreak contacts of relay 1.00 and the left hand winding ol' relay 101 to hattery. This relay is therel'orc maintained operated. ()n the operation of relay ltltl. the circuit for relay 102 is opened at. the outer lelt hand armature and hack contact ol' this relay and relay ltiQ in releasing causes the release of rd lay ltl-Tl and relay ltlil releases relay ltlO. ()n

the release of relay ltlt the original circuit for lamp 12 is reestablished so that thislamp again lighted and the operation and release of relays 100, 102 and 103 are repeated in this manner so as to alternately light and extinguish lamp 12. The flashing of lamp 1; indicates to the B operator in charge of trunk ST that a connection over this trunk is desired.

The operation of relay 9 also closes at its outer right hand armature and trout con tact a circuit tor the operation of the pilot relay to and this relay in operating lights pilot lamp lti. Another circuit is also partially prepared hy the operation of relay t! for the suhserptent operation of relay 1 a will hereinafter he descrihed.

'l'he ll operator now deprcsres key it) to associate the common ringing key equipment and her telephone set with this trunk. The operation ol key it? closes the circuit previously prepared hy the operation 01f relay 9 tor the operation oi relay 18 as l'ollows'. hattcry. make-hel'ore-hrcak contacts of relay ltl. inner lel t hand 111i!lit'l)t?l t)ltf-l)l't'ttl contacts of relay 11, left hand inner armatitre and front contact ol. relay 9, winding of relay ltw and left hand winding of: relay 9 in parallel therewith. key 2 lctt hand outer armature and back contact. oi. relay lead left hand armature and back contact o l relay 105. left hand armature and back contact of relay 106 to ground. The operation of relay causes an obvious circuit to he closed for the operation of relay This relay in operating provides a lock ing circuit- 't'or itsclt as follows: l att'cry. make-hetore-hrcak contacts of relay to. right hand armature and front contact and right hand winding of relay 22, lower inner armature and break contact of relay 7, ground at the armature and front contact of relay The operation of relay 22 opens the original energizing circuit for relay '18 through lceyflth The operation of relay 22 also causes other connectit'ms to h made. the purpose of which will become. apparent athe description proceeds. Relay 18 in opcratin provides a lfit'lillltf circuit for itself independent of the circuit through key it) over its upper inner armature and trout. contact through lead 25, winding of relay 10S, armature and hack contact of relay 10!) to ground. ltelay 1H8 operates in this circuit and lights lamp lttl which indicates that this conunon ringing key equipment will he used by the li operator. For a more complete description ol the specilic, purpose of lamp ll l, rel'crcncc may he had to the copcnding application ol' llorace ll". l ll'ich. mentioned ttlltH't'. 'lhc operation of relay .l lH eatlstH an ohrious circuit to he. closed for the operation ol' relay tilt; and relay lot. in operatin 1 t'lo cs a circuit. for the operation of relay lli. llelay 112 in operating closes a circuit tor the lighting of lamp 113 which lamp now indicates to the it operator that her telephone set 115 and the common ringing key equipment generally indicated by the numeral l'lt' have been connected to a trunk such as ST.

it will he noted that the operation of relay ltlti removes the ground at its left hand armature and hack contact to lead 23 for the original energizing circuit of relay .18 and as this lead 2 3 is common to all trunks in the group of which trunk ST is one. the common ringing key equipment and the operator's teltqihone set cannot be associated with any other trunk in this group as long as relay lb of trunk ST is operated, that; is, only one trunk at a time can be associated with this common equipment.

It will now he described in more detail how the [3" operators telephone set 1153 and the ringing key equipment are connected to the trunk .i'l and how a signal is transmitted to the toll operators cord 1 at A. to indicate that the li operator is now ready to re cciye the information relating to the extension of a call.

This signal consists of two successive anplications of tone current. from a source 118. llpon the operation ol' relay it"; the circuit is closed for the operation ol' relay 119 as follows: battery. windin; of relay 1.19. lower outer armature and hack conta t of relay 12H. lower outer armature and front contact ol relay 12,1. lel't hand armature and front contact of relay ton to ground. lt is noted that this circuit is traced through the lower outer armature and trout contact ol relay 121. It is evident that lay examining the circuits that this relay is operated as soon as the operators telephone set 115 is connected to jacks and plugs 122 to the repeating coil 123. That is. when this connection is made a circuit is completed for the operation of relay 124 through the operators transmitter. The operation of relay 19. 1

closes an obvious circuit for the operation of relay 121. Hence these two relays remain operated as long as the operators telephone set is connected at this point. The relay 119 in operating connects the secondary winding of repeating coil 126 to the tip and ring leads now connected through the operation of relay 18 to the conductors of trunk ST. This circuit may be traced from the tip and ring conductors of trunk ST hrough the upper outer and lower outer armaturcs and front contacts of relay 18, tip and ring conductors 27 and 28, upper outer and lower in- :ner armatu-res and back contacts of relays 120 and 127 upper outer and lower inner armatures and front contacts of relay 119 to the secondary winding of repeating coil 126. The primary winding of this repeating coil is connected by the operation of relay 119 as follows: ground, secondary winding of repeating coil 128, primary winding of repeating coil 126, lower outer armature and front contact of relay 119, niake-before-break contacts of relay 130, lower ari'nature and back contact of relay 131, upper inner armature and back contact of relay 127 to ground at the inne-r upper armature and front contact of relay 119. The secondary winding of repeating coil 128 is associated with the tone source 118 so that an impulse of tone current is now transmitted from this source through trunk ST to the toll operators telephone set connected to cord 1. The operation of relay 119 also closes an obvious circuit for slowtooperatc relay 130. hen this relay operates it opens the circuit for the primary winding of repeating coil 128 and secondary.

winding of repeating coil 126 so that the impulse of tone current applied through these windings to the trunk ST is cut off. The operation of relay 130 also closes an ob vious circuit for the operation of slow-tooperate relay 132. Relay 132 in operating again closes a circuit for the coupling between the tone source 118 and the secondary winding of repeating coil 126 by closing a circuitthat now extends through the lower armature and front contact of relay 130, the lower armature and front contact of relay 132 through the lower armature and back contact of relay 131. Hence a second application ofrtone current from source 118 is now effected. Relay 132 also closes an obvious circuit for the operation of the slow-to pers ate relay 131. On the operation of relay 1311, the circuit for the secondary winding of repeating coil 128 and the primary winding of repeating coil 126 is again opened, this time 'at the lower armature and back contact of relay 131. Consequently, the second impulse of tone current is thereby re moved Irom the trunk.

The operation of relay 131 closes an obvious circuit-for the operation of relay 127 and this relay in operating-closes a locking circuit for itself to ground at the upper inner armature and front contact of relay 119.

Relay 127 operated opens the connection from thesecondary winding of repeating coil .126 to the tip' and ring contacts of the trunk and also the circuit through the secondary winding of repeating coil 128 and primary winding of repeating coil 126. As long as relay 119 is operated no further application of tone current will therefore be made during the connectionof the circuits shown in Fig. 2 to the trunk' ST. On the operation of relay 127 the operators telephone set 115 is connected through the repeating coil 123 to the tip and ring conductors of trunk ST at the upper outer and inner lower armatures and front contacts of relay 127. 9 y

The operation of relay 18 connects certain otherleads between the common ringing equipment and the trunk ST such as loads 36 and 37 and the operation of relay as hereinhefore mentioned, connects lead 38. These three leads are for the purpose of controlling the ringing equipment associated with the trunk through the manipulation of the ringing keys 116.

As the B operators telephone set is now connected to the trunk and the toll operator at A has received a signalto this effect, this latter operator will pass the information relative to the extension of a connection by the B operator. lVhen this information is received, the B operator willoperate the COII'GSPOIlCllllg key in the ringing key equipment. If the party wanted is one on a party line, one of the keys 140, 14:1, 142 or 143 is operated whereas if the Wanted subscriber is on a private line key 14 1 is operated. If it is decided to ring party M, key 140 is depressed to prepare the ringing equipment associated with the trunk ST for the sending of the propel-signal when plug 40 of trunk ST is inserted in jack 41 of the party line 3. hen key 1410 is depressed relay 146 is actuated over an obvious circuit; This relay in operating prepares a locking circuit for itself through its right hand armature and frontcontact to ground at the inner left hand armature and front contact of relay 112. On the operation of relay 146 circuits are completed for the operation of relays 43 and 41. The circuitfor relay 43 may be traced as followsz'battery, winding of relay 13, lower1niddle armature and front contact ofrelay 18, lead 36, left hand armature and front contact of relay "116 to ground atrelay 112, while the circuit for relay 44; extends from battery through the; winding of relay ea, left hand inner armature and front con tact of relay 22, conductor 88, left hand armature andjfront contact of relay 146 to ground at relay 112. Relays 43 and 41pm: pare obvious locking, circuits for themselves to ground that will be supplied at the left- IOU hand middle armature and front contact of relay 11, when this latter relay operates as hereinafter described. The operation of relays 1-3 and i l causes the current from the ringing, source at; to be connected for application to the tip conductor of trunk ST. The circuit in this instance may be traced as follows: Ringing source 4.6. right hand inner armature and right hand outer armature and front contacts of relay l3, left hand inner armature and front contact of relay l t to the upper outer armature and front contact of relay 1?, while the operation of relay 44 connects ground for application to the ring conductor of trunk ST as follows: ground, right hand armature and front contact of relay 44 to the front contact associated with the lower armature of relay 47.

It should be noted that operation of relay 116 also closes a circuit for the operation of the slow-to-ope"at r lay 117 as follows: battery. winding of relay 147. right hand armature and a front contact of relay 146 to ground at the inner left hand armature and front contact of relay 112. This relay in operating closes a circuit to battery for the operation of relay 11 as follows: battery. right hand armature and front contact of relay 147. inner right hand armature and front contact of relay 112, lead 37, inner lower armature andfront contact of relay 18. left hand winding of relay 11, armature and front contact of relay 8 to ground. Relay it in operating prepares a. locking circuit for itself through the right hand winding to be subsequently closed on the operation of relay 7 and a locking circuit through the left hand winding to battery at makc-before-lnrcak contacts of relay 10. This relay also completes at its left hand middle armature and front contact the above mentioned locking circuit to ground for relays 43 and 44. The operation of relay 11 by opening its make-before-break contacts to the battery at the make-before-break contacts of relay opens the energizing circuit for the relays 9 and 18. which will. now be released to disconnect the leads 25. 37 and 36 from the trunk ST to disconnect the common ringing key equipment from the trunk.

The operation of relay 146 therefore prepares the ringing equipment associated with trunk ST for the transmission of the signal for calling part-y M on the desired line. when the trunk ST is connected thereto.

Relay 9 in releasing opens the flashing circuit for the guard lamp 12 through the equipment shown in Fig. 2. so that this lamp will now be lighted steadily over a circuit as follows battery. lamp 12, inner right hand armature and back contact of relay 9. lower outer armature and back contact of e ay ute ef han a m ture and front contact of relay 11, winding of pilot relay 15 to ground. This causes the maintenance of the operation of pilot relay l5 and the lighting of lamp 12 steadily. The steady lighting of lamp 12 indicates to the B operator that the signaling equipment associated with the trunk ST has been set in accordance with the operation of a ringing key.

It t ident from the above description of the operation of the ringing hey equipment that the operation of any of the other ringing keys ll], 14-2 or 143 will set up similar conditions in the ringing equipment of trunk ST by causing the operation of either of relays 43 and ll in connection with relay 11 or the operation of relay ll alone and that the operation of trunk hey l-ll; will cause no operation at all of any of these rc lays. The operation of key lll will simply release the ringing key equipment from the trunk ST.

As stated. lamp 12 is now lighted steadily to indicate that the trunk is ready for extension to the wanted subscrihens line. Hence. the operator will now insert plug into jack ell of the desired line 3. This causes the operation of relay 7 over the sleeve circuit. The operation of relay 7 extends the tip conductor of trunk ST through the upper armature and back contact of relay -17 to ground at the repeating coil 4!). The. operation of this relay also extinguishcs the guard lamp 1.2 and pilot lamp it; by opening thev connection for these lamps through its lower armature and back contact. The operation of this 1'ela also closes a circuit for the release of relays 22 and ti. llclay 2:2 is released by the opening of the cr'nuieclion at the lower inner armature and back contact of relay 7, while relay ('1 is released by opening the connection at the upper inner armature and back contact of relay 7. lclay remains operated over the loop in the toll operators cord 1. A second locking circuit. is provided for relay 11 on the operation of relay 7 as follows: battery. upper inner armature and front contact of relay 7. right hand armature and front contact and right hand winding of relay 11 to ground. The purpose of this locking circuit will become apparent as the description proceeds. The battery at the upper inner armature and front contact of relay 1' is also connected to the winding of relay 4-? for the operation of this relay later. as will hereinafter be de scribed. The release of relay 6 causes battery and ground through the windings of relay 5 to be connected at the repeating coil 49 fortrunl: ST to cause the lighting of the usual supervisory signal in the toll operators cord circuit to indicate to this operator that the ringing equipment in trunk ST has been set ready for the transmission of a ringing signal to the wanted subscriber.

The toll operator may now operate her llll lilli ill-3 ringing key to transmit an alternating current signal over the trunk ST for the oper ation of the"ringing'equipment as follows: This signal causes the operation of relay 50 and relay 50 in operating completes the above mentioned circuit for relay by establishing a connection to groui'id through its armature and front contact. Relay 47 in operating applies the prepared ringing signal to the tip and ring conductors of the trunk over plug 10' and'jack 41 to line In this case partyM is the party desired, hence ringing current from source 46 is applied to the tip conductor and ground to the ring conductor. The operation of relay 4-7 causes the operation of relay 6 over an obvious circuit during the ringing period to prevent relays 5and S from releasing to light lamp 12 asa disconnect signal during the ringing period. It will be observed that a circuit was partly closed for this lamp through the operation of relay 7 at the lower outer armature and front contact of this relay and in case relay 8 were to release during this period this circuit would be completed at the make-before-break contacts of this re lay.

WVhen the wanted subscriber answers this call by removing his receiver from the hook and when the toll operator stopsringing. the relay 51'will operate as on the release of relay fii', due to the release of relay 50, the circuit is completed for relay 51 to the re peating coil 49' and the subscribers loop. Relayf51 causes the operation of relay 6 as followsi battery, right hand winding of relay 6, armature and frontcontact of relay 51 to grouikl at the armature and front contact of relay 5. RelayG inoperating causes the supervisory lamp in the toll operators cord 1 to be extinguished as a signal that the called subscriber has answered. Conver sation'inay now begin, that is, as soon as the toll operator has completed the connection to the calling subscriber in a manner well known in the art. It: the toll operator has discontinued to send a ringing signal before the wanted subscriber answers, relay (twill release to operate the supervisory signal to indicate this condition to the toll operator.

WVhen the receiver is replaced on the switchhook at the end of conversation at the called subscribers station, relay 51 releases, causing the release of relay 6. Relay 6 in releasing causes the supervisory lamp at the toll operators position to light as a disconnect signal. \Vhen the plug of cord 1 is removed from jack 2 'of trunk ST, relay 5 is released. This relay in turn releases relay 8 and the above mentioned c rcuit for lamp 12 is completed at the make-before-break contacts of this relay to cause this lamp to be lighted as a disconnect signal. The B operator will now remove plug 40 from jack 41, causing the release of relay to extinguish the lamp l2 and release and 44.

As is well known in the art, the B operator may test the wanted subscribers line by touching the sleeve of jack 41 with the tip of plug 40 and if the wanted subscriber is busy she will receive a busy signal through the lead 55 and winding 149 of coil 123. If the wanted subscribers line is found ,busy, the B operator may notify the toll operator at Aof this fact by sending a busy back tone signal to this operators telephone and to cause the flashing of the supervisory lamp in, cord 1 as a busy back signal for this cord. The busy back tone may be applied as follows: The busy back key 150 which is common to the group of trunks at the B operatofis position, will when depressed initiate the transmission of thebusy back tone and busy back cord signals. This key may be operated before or after the common ringing key equipment is actuated.

If the key is operated before the ringing key equipment is operated, it will not only cause the transmission of the busy back ton'e and busy back cord signals, but also release the ringing key equipment and the B operators telephone set from the trunk ST. .The operation of key 150 causes the operation of relay 105. This relay -in operating applies battery through its left hand winding and left hand armature andfront contact to lead 23 tocause the operation of: the busy back be traced through the left hand outer armatureand front contact of relay 22' and left winding of busy back relay 10 to ground. It shouldbe noted that relay 22 is held operated at this time'through an obvious circuit maintained by relay 18. Relay 10 in operating provides a locking circuit for itself through its right winding as follows: battery, right hand armature and front contact and right hand winding of relay it), in mature and front contact of relay 8 to ground. Relay '10 applies a tone current from an alternating current source connected to leads. 5st to the tip and ring conductors of the trunk ST. This ringing tone is transmitted through the repeating coil 1-9 to the toll operators telephone at A.

relays 11, 43

Belay 1:0 in operating also causes the tlasln 1 terrupter 56 to ground connected through the lower inner armature and front contact of relay 10, so that relay 6 is alternately operated and released to alternately connect battery and ground to the trunk ST and this causes as is well known the flashing of the supervisory lamp in cord 1. The operation of relay 10 also by opening its make-beforebreak contacts removes battery from the locking circuits for relays 22, 18 and 5), so that these relays release. Relay 18 in re leasing removes the common ringing kcy equipment and the B operators telephone set from the trunk ST and relay 9 in releasing extinguishes the lamp 12.

If the key 150 is operated after the ringing key equipment is operated, relay 10 will release relays 22 and 11 and relay 11 will cause the release of either or both of the relays 43 and -11 it operated and thus restore the ringing equipment to normal. Relay 10 is released when a toll operator removes her plug from jack 2 of trunk ST by the release of relay 8.

The operation of the peg count meter 152 will now be described. This meter will operate on the operation of any of the ringing keys at 116 or on the operation of the busy back key 150, if this key is operated before the key in the ringing key equipment is operated, but will not operate on the operation of ringing key 150 if it is operated after a key in the ringing key equipment has been operated. Thus, the operation of the peg count meter can only be effected once during each connection of the ringing key equipment to a trunk.

The operation of the meter 152 on the operation of a ringing key such as, for example, key 1 10 is established through the operation of relay 14-7. It has already been shown how relay 117 is operated in this case and the circuit for meter 152 is completed as follows: battery, Winding of meter 152, outer left hand armature and front contact of relay 147, outer left hand armature and front contact of relay 112 to ground. If trunk key 144 is operated relay 153 is actuated over an obvious circuit and the circuit for meter 152 in this case is as follows. battery, Winding of meter 152, outer right hand armature and front contact of relay 153, outer left hand armature and front contact of relay 112 to ground.

If the busy hack key is operated before a key in the ringing key equipment is operated, relay 105 in operating Will close a circuit for the operation of the meter 152 as follows: battery, winding of meter 152, right hand armature and front contact of relay 105. middleleft hand armature and front contact of relay 112 to ground. If the busy hack key 150 is operated after the operation of a key in the common ringing key equipment, this circuit completed through the lower armature and front contact of relay 105, will not be completed through the mc ter 152, as relay 112 will be released at this time.

It should be understood that the particular system shown merely illustrates one application of the invention and that the invention could be applied to other systems Without departing from the spirit thereof.

lVhat is claimed is:

1. In a telephone system, a plurality of lines, a set of common control keys for said lines, a key individual to each of said lines, a meter common to said lines. means responsive to the initiation oi. a. :all over said line and to the operation of the corresponding key for connecting said common control keys to said line, and means for actuating said meter responsive to the actuation of any one of said common control keys.

2. In a telephone system, a plurality of lines, a. set of common control keys for said lines, a key individual to each of said lines, a meter common to said lines. means responsive to the initiation of a call over said line and to the operation of the corresponding key for connecting said common control keys to said line, means for transmitting a busy signal back over said line, and means for actuating said meter in response to the actuation of said signal transmitting means.

3. In a telephone system, a plurality of lines, a. common control equipment for said lines, a key individual to each of said lines, a. meter common to said lines, means responsive to theinitiation of a call over said line and to the operation of the corresponding key for connecting said common control equipment to said line, means for transmitting a busy signal back over said line, and means for actuating said meter either in response to the actuation of the common control equipment or to the actuation of the signal transmitting n'ieans.

4. In a telephone system, a plurality of lines. a common control equipment for said lines, a key individual to each of said lines, a. meter con'nnon to said lines. means respoin sive to the initiation ol a call over said lino and to the operation of the correspondin; key for connecting said common control equipment to said line, means for transmit ting a busy signal back over said line and means for actuating said meter in response to the actuation of the signal transmitting means before the common control equipment is actuated.

In Witness whereof, I hereunto subscribe my name this 24.- day of May A. D., 1927.

CLARENCE B. FOlVLER. CHARLES W. LUCEK.

Illa. 

